A method for adhering a base material that has low surface energy, such as polyethylene and polypropylene, has been studied, and designing an adhesive that has excellent adhesion to such a material has been known to be difficult. As a method for providing excellent adhesion to such a base material with low surface energy, one suggestion has been a technique in which the surface of a body to be adhered to is pre-treated with corona discharge, plasma treatment, etc., to increase the surface energy, followed by adhesion. While such a method is an effective technique, expensive equipment is required and power consumption increases.
Recently, products using olefin-based materials such as polyethylene and polypropylene are increasing in various applications such as for household articles around us and for industrial applications. In particular, in applications for vehicles, application of a molding material containing polypropylene as a material has been actively promoted in the trend toward automobile weight reduction. From such circumstances, effective adhesives that had been previously unavailable have been recently developed. This is also disclosed in Non-patent Literature 1 on page 139 under “2.1 State of Adhesion Techniques.” Specific examples of the adhesive include those disclosed in Patent Literature 1 and 2. In addition, due to problems in the work environment, adhesives have been recently changing from conventional organic solvent adhesives to aqueous adhesives, which are more environmentally friendly. The examples are disclosed, for example, in Patent Literatures 3 to 5.